xi ARTI01DACTYLES OF MADAGASCAR 273 in Europe, Asia, and Africa. The -Neotropical region has no Oxen,, or Sheep, or Antelopes. The latter are confined to Africa, Asia, and certain parts of the Falaearctic region- ; they are vastly more prevalent in Africa, where they take the place of the totally absent Deer. The Pig tribe is almost entirely Oriental and Ethiopian in distribution, only one form, the European Wild Boar, ranging into the Palaearctic region; and the two species of Peccary are found in both North and South America. Broadly speaking, the Ethiopian region is the headquarters of the Artio- dacfeyla. But the great island of Madagascar lias but one form of Artiodactyle, a Pig of the genus JPotamoehoemts.1 GROUP I.—SUINA. Fam. 1. Hippopotamidae.—The family Hippopotamidae con- tains of existing genera only Hippopotamus, for the Liberian dwarf Hippopotamus is not now regarded, as it was formerly, as the type of another genus, Ohoeropsis, The reasons for its former separa- tion were the loss of the outer pair of incisors and the different proportions of various parts of the skull. This little Liberian animal has, however, been shown by Six W. Flower2 to possess the missing incisors occasionally; and as to the proportions of the skull, it is exceedingly common for small animals to vary from larger relatives in this way. Hence, considering the characteristic features of the Hippopotamus and the fewness of species, it seems unnecessary to divide it up further. We shall therefore only recognise one genus. The Hippopotamus at present is African in range, and confined to that continent. But quite recently it inhabited Madagascar; and further back still in time the existing African species, H. amphibius, ranged into Europe ; there were also Indian forms, which were contemporary with the Stone-age man. The Common Hippopotamus is a great thick-skinned beast with but few hairs. It has four toes on each foot, a complex stomach, but no caecum. The strong incisors continue growing through life, as do the great canines. The number of incisors is two on each side of each jaw. Some of the extinct species had six in each 1 Bones of Hippopotamus, however, indicate the very recent occurrence of that animal in Madagascar. 2 **On the Pvarmv HiiynoTiotaimis of I^iberia.fi Prac* Z&ol. jS&e. 1887. t>_ 612.